The M16-style rifle is a type of modular rifle system commonly used by military and police forces that features a gas-operated bolt and bolt carrier system, as disclosed, for example, in U.S. Pat. No. 2,951,424, issued to Eugene M. Stoner on Sep. 6, 1960 (incorporated herein by reference in its entirety). A modular rifle typically includes a lower receiver assembly, and upper receiver assembly, and a coupling mechanism. Two types of M-16-style rifle are the M16/M4 rifle system in 5.56 mm/.223 caliber and the AR10/SR25 rifle system in 7.62 mm/.308 caliber. The M16/M4 rifle system in 5.56 mm/.223 caliber and the AR10/SR25 rifle system in 7.62 mm/.308 caliber each utilize direct gas operation with a traditional, non-folding butt stock. The current designs of the M16/M4 and AR10/SR25 rifle systems contain a recoil spring and buffer assembly, which allows the bolt carrier to cycle when the rifle is being fired. These recoil springs and buffer assemblies are typically contained with the rifle in the same center line as the barrel, requiring the traditional fixed stock in order to contain the spring and buffer assembly and allow for compression of the spring and cycling of the bolt carrier. Relocating the recoil spring and rod outside of the center line of the barrel allows for the M16-style rifle to have a folding or non-fixed stock. Containing the relocated recoil spring and rod within a housing further prevents the detrimental effects of heat transfer from the direct gas operation.